Alveolar Arch

The aim of this study was to compare the transverse dimensions of the dental arches and alveolar arches in the canine, premolar, and molar regions of Class II division 1 and Class II division 2 malocclusion groups with normal occlusion subjects. This study was performed using measurements on dental casts of 150 normal occlusion (mean age: 21.6 2.6 years), 106 Class II division 1 (mean age: 17.2 2.4 years), and 108 Class II division 2 (mean age: 18.5 2.9 years) malocclusion subjects. Independent-samples t-test was applied for comparisons of the groups. These findings indicate that the maxillary interpremolar width, maxillary canine, premolar and molar alveolar widths, and mandibular premolar and molar alveolar widths were significantly narrower in subjects with Class II division 1 malocclusion than in the normal occlusion sample. The maxillary interpremolar width, canine and premolar alveolar widths, and all mandibular alveolar widths were significantly narrower in the Class II division 2 group than in the normal occlusion sample. The mandibular intercanine and interpremolar widths were narrower and the maxillary intermolar width measurement was larger in the Class II division 2 subjects when compared with the Class II division 1 subjects. Maxillary molar teeth in subjects with Class II division 1 malocclusions tend to incline to the buccal to compensate the insufficient alveolar base. For that reason, rapid maxillary expansion rather than slow expansion may be considered before or during the treatment of Class II division 1 patients.

alveolar arch

Download File: https://www.google.com/url?q=https%3A%2F%2Fmiimms.com%2F2uirH2&sa=D&sntz=1&usg=AOvVaw0hq_F9qXTb8GoItKtLFDGL

Fröhlich4 compared intercanine and intermolar widths of both arches from 51 children with Class II malocclusion with normal occlusion. He found that the absolute arch widths of the Class II children did not differ appreciably from those of children with normal occlusion. Sayin and Turkkahraman5 compared the arch and alveolar widths of patients with Class II division 1 malocclusion and subjects with Class I ideal occlusion in the permanent dentition. They indicated that mandibular intercanine widths were significantly larger in the Class II division 1 group, although maxillary intermolar widths were larger in the normal occlusion sample. Staley et al6 stated that patients with Class II division 1 malocclusion had narrower maxillary intercanine, intermolar, and alveolar widths. Their findings revealed a posterior crossbite tendency in the Class II group. Enlow and Hans7 discussed generic Class II skeletodental features and facial growth without differentiating Class II division 2 from Class II division 1 and reported that Class II patients have long, narrow anterior cranial bases that affect the nasomaxillary complex and result in long, narrow palates and maxillary arches.

In a cross-sectional study of 386 white women, Buschang et al8 found that Class II division 2 patients had greater maxillary intercanine and intermolar distances than did Class II division 1 patients. However, the Class II division 2 patients showed less mandibular intercanine and intermolar width than the Class I and II division 1 patients. Moorrees et al9 used serial dental casts of untreated Class II malocclusions to compare arch dimensions of Class II division 1 and Class II division 2 subgroups. Compared with dental cast measurements from a control reference population, Class II division 2 dental casts had maxillary and mandibular intercanine distances greater than average and normally distributed intermolar distances.

Most of these studies presented a limited sample size resulting in questionable validity. Therefore, the aim of this study was to compare the transverse dimensions of the dental arches and alveolar widths of Class II division 1 and Class II division 2 malocclusion groups with the transverse measurements of untreated normal occlusion subjects. The null hypothesis to be tested states that there is no difference in the mean maxillary and mandibular dental arch and alveolar width dimensions among Class II division 1, Class II division 2, and a normal occlusion sample.

This study was performed using the dental casts of 150 normal occlusion, 106 Class II division 1, and 108 Class II division 2 malocclusion subjects from the archives of the Selcuk University, Faculty of Dentistry, Department of Orthodontics. The distribution of age in different malocclusion groups for all subjects is shown in Table 1.

Twelve arch width measurements were recorded from each subject's dental casts by one examiner (Dr Memili) using a dial caliper and recording the data to the nearest 0.1 mm. These measurements are shown in Table 2.

Descriptive statistics (mean, standard deviation, minimum and maximum) and statistical comparisons of dental and alveolar width measurements for dental casts in the three groups (normal occlusion, Class II division 1, and Class II division 2) are shown in Table 4. According to the independent-samples t-test, statistically significant differences were found in maxillary and mandibular dental arch and alveolar width dimensions among Class II division 1, Class II division 2, and normal occlusion samples. The null hypothesis was thus rejected.

Statistically significant differences were found in nine of the 12 measurements. The maxillary interpremolar width (P

Table 4 shows the statistical comparisons of the normal occlusion and Class II division 2 malocclusion samples. Normal occlusion subjects had statistically significant narrower lower intercanine and intermolar widths (P

This study was carried out to compare the dental arch and alveolar base widths of Class II division 1 and Class II division 2 malocclusion groups with an untreated normal occlusion sample. Width measurements described in this article will help clinicians diagnose and plan the treatment of patients with Class II division 1 and Class II division 2 malocclusions.

The large sample size in this study might have increased its power. An increased sample size leads to a greater probability of establishing statistical significance for the observed trends in all dental and alveolar width measurements.

In the normal occlusion sample only subjects with minor or no crowding were included, whereas the absence of crowding was not a criterion in the Class II groups. If a Class I group with crowding would be compared with a Class I group without crowding, most probably narrower arches would be found in the Class I group with crowding. For that reason, group differences in this study may be the result of differences concerning crowding as well and our results must be interpreted carefully.

Clinicians have speculated that nasal obstruction, finger habits, tongue thrusting, low tongue position, and abnormal swallowing and sucking behaviors were reasons for narrower maxillary dental arch widths in Class II division 1 malocclusions compared with a normal occlusion sample. Staley et al6 stated that the maxillary dental arch as a whole is narrower in adults with Class II division 1 malocclusion than it is in adults with normal occlusion. When we compare the dental and alveolar arch widths of Class II division 1 malocclusion samples with the normal occlusion samples, statistically significant lower values were found in most of the upper arch widths in Class II division 1 patients. All upper alveolar width and interpremolar width measurements were greater in the normal occlusion sample. However, the intermolar dental arch width was larger in the Class II division 1 sample.

Staley et al6 reported that subjects with normal occlusion had larger maxillary canine widths than the malocclusion subjects, but no differences were found in mandibular canine widths. Bishara et al17 studied the growth trends in maxillary and mandibular dental arch widths and lengths in persons with Class II division 1 malocclusions and normal subjects and reported no differences in maxillary and mandibular canine width measurements between the groups. In contrast with the others, Sayin and Turkkahraman5 found that mandibular intercanine widths were significantly larger in the Class II division 1 group than in the Class I group, whereas no significant differences were found among maxillary intercanine width measurements. In accordance with Sayin and Turkkahraman,5 the results of this study showed that the maxillary intercanine width difference was similar in Class I and Class II division 1 groups, and the mandibular intercanine width was significantly larger in the Class II division 1 sample. Both these investigations were carried out on the same population and it could be the specific peculiarity of this population (Figures 1 and 2).

In this study, molar reference points were taken from Staley et al,6 who measured the widths between the mesiobuccal cusp tips of the maxillary first molars and the buccal grooves of the lower first molars. Because, in normal centric occlusion, the mesiobuccal cusp tips of the maxillary molars are positioned near the buccal grooves of the mandibular molars. Staley et al6 and Sayin and Turkkahraman5 suggested that the narrow widths of the dental arch in Class II division 1 patients appeared to be caused by palatally tipped teeth and also by narrower bony bases of the dental arch. Their results showed that transverse discrepancy in Class II division 1 patients originated from upper posterior teeth and not from the maxillary alveolar base. 041b061a72